function User(name) {
    this.name = name;
    this.sayHi = function () {
      console.log("My name is: " + this.name);
    };
  }
  // 使用new关键字，调用构造方法User，创建User对象peter，name为'Peter'
  let peter = new User("Peter");
  // 调用peter对象的sayHi方法
   peter.sayHi();
  // 练习5
